Current HIV vaccine candidates elicit reasonably potent cellular immune responses, but only low levels of neutralizing antibodies. Such CTL based vaccines (e.g., those based on DNA immunization) do not prevent infection, but can have a beneficial effect on disease course. In contrast, passively infused antibodies can provide complete protection, but must be administered in doses that result in serum antibody levels much higher than can be generated by current immunization strategies. We are studying the effect of passively transferred neutralizing antibodies alone, or in combination with active cellular immunity inducted by vaccination.